Flame-resistant fabrics (also variously referred to as “fire-resistant,” “flame-retardant,” and “fire-retardant” fabrics) are fabrics that, once ignited, tend not to sustain a flame when the source of ignition is removed. Considerable research has been directed toward the development and improvement of flame-resistant fabrics for use in various products, including clothing and bedding. Flame-resistant clothing is often worn by workers involved in activities such as industrial manufacturing and processing (such as oil, gas, and steel industries), fire-fighting, electrical utility work, military work, and other endeavors that entail a significant risk of being exposed to open flame, flash fire, momentary electrical arcs, and/or molten metal splash. Non-flame resistant work clothes can ignite and will continue to burn even after the source of ignition has been removed. Untreated natural fabrics will continue to burn until the fabric is totally consumed and non-flame resistant synthetic fabrics will burn with melting and dripping causing severe contact burns to the skin. the majority of severe and fatal burn injuries are due to the individual's clothing igniting and continuing to burn, not by the exposure itself. The abrasion resistance of protective fabrics is also an important performance property, as garments which develop failures, such as holes and rips, can compromise the protective properties of the fabric.
Flame-resistant fabrics include both fabrics that are treated to be flame-resistant as well as flame-resistant fabrics made from inherently flame-resistant fibers. The former types of fabrics are not themselves flame-resistant, but are made flame-resistant by applying to the fabric a chemical composition that renders the fabric resistant to flame. These types of fabrics are susceptible to losing their flame-resistance with repeated laundering because the flame-resistant composition tends to wash out. In contrast, inherently flame-resistant fabrics do not suffer from this drawback because they are made from fibers that are themselves flame-resistant. The use of flame resistant clothing provides thermal protection at the exposure area. The level of protection typically rests in the fabric weight and composition. After the source of the ignition is removed, flame resistant garments will self-extinguish, limiting the body burn percentage.
Various types of inherently flame-resistant (FR) fibers have been developed, including modacrylic fibers (e.g., modacrylic fibers sold under the PROTEX name from Kaneka Corporation of Osaka, Japan), aramid fibers (e.g., meta-aramid fibers sold under the NOMEX name and para-aramid fibers sold under the KEVLAR name, both from E.I. Du Pont de Nemours and Company of Wilmington, Del.), FR rayon fibers, oxidized polyacrylonitrile fibers, and others. It is common to blend one or more types of FR staple fibers with one or more other types of non-FR staple fibers to produce a fiber blend from which yarn is spun, the yarn then being knitted or woven into fabrics for various applications. In such a fiber blend, the FR fibers render the blend flame-resistant even though some fibers in the blend may themselves be non-FR fibers, because when the FR fibers combust they release non-combustible gases that tend to displace oxygen and thereby extinguish any flame.
For example, US 2005/0025963 discloses an intimate blend of staple fibers having 10 to 75 parts by weight of at least one aramid fiber, 15 to 85 parts by weight of at least one modacrylic fiber, and 5 to 30 parts by weight of at least one polyamide fiber. Another blend of staple fibers is disclosed in US 2004/0192134, including at least about 60 percent FR fibers (modacrylic and/or aramid) and up to 40 percent synthetic or natural non-FR fibers such as cotton or wool. U.S. Pat. No. 6,787,228 discloses a yarn formed of a blend of fibers including at least about 70 percent modacrylic fibers combined with at least about 3 percent high-performance, high-energy-absorptive fibers such as aramid.
ASTM F1930-99 is a full-scale mannequin test designed to test fabrics in completed garment form in a simulated flash fire. A mannequin, with up to 122 heat sensors spaced around its body, is dressed in the test garment, and then exposed to a flash fire for a pre-determined length of time. Tests are usually conducted at heat energies of 1.8-2 cal/cm2sec, and for durations of 2.5 to 5.0 seconds for single layer garments. Results are reported in percentage of body burn. For consistency in data and accuracy of comparison, the test method defines a standard garment size and configuration that must be used on each test.
In addition to the above-noted performance specifications of fabrics, other properties are also important if a fabric is to be practical and commercially viable, particularly for clothing. For instance, the fabric should be durable under repeated industrial launderings and should have good abrasion-resistance. Furthermore, the fabric should be comfortable to wear. Unfortunately, many of the FR blends are not comfortable under typical environmental conditions. In such cases, wearers tend to be less likely to be compliant and thereby decreasing the probability that the wearer will continue to use the garment as intended. Thus, it is beneficial if an FR fabric exhibits good moisture management properties, i.e., ability to wick away sweat and dry quickly so that the wearer does not become overheated or chilled, and/or the fabric does not irritate the wearer's skin.
There exists a need for a fiber blend that is not only fire-resistant but also provides superior moisture management properties and strength properties to ensure wearer compliance. The fiber blends, fabrics, and garments of the present invention are directed toward these, as well as other, important ends.